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Addressing I/Os
CPU 948 Programming Guide
C79000-G8576-C848-04
You can use load and transfer operations to address the I/O peripherals
as follows:
• • directly using the following operations:
L../T.. ..PY, ..PW, ..OY, ..OW
or
• • using the process image with the following operations:
L../T.. ..IB, ..IW, ..ID, .QB, ..QW, ..QD
and with logic and set/reset operations
Note
If you use the transfer operations T PY 0 to 127 and T PW 0 to
126, the process output image is updated at the same time.
Exception: command output is disabled by the STEP 5 operation
BAS (refer to Section 3.5.4).
Note the following points about I/O peripherals:
• • A process input/output image exists for 128 input and 128 output
bytes of the P peripherals with byte addresses from 0 to 127.
• • No process image exists for the entire area of the O peripherals and
the P peripherals with relative byte addresses from 128 to 256.
(For more information on address space allocation see
Section 8.2.2).
• • I/O modules with addresses of the O peripherals can only be plug-
ged into expansion units (not in the central controller).
• • In one expansion unit, you can use either only P peripherals or
only O peripherals.
Caution
If you use relative addresses of the O peripherals in an expansion
unit, you can no longer use these addresses for I/O modules in the
central controller (this would result in double addressing).
Basic Operations
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